Engine swap '04 Tahoe 5.3 to 6.0

[mattt]

Thanks Rocket Man for the suggestion. As it turns out, right about the time that you posted that reply, I pulled a spare Escalade cluster that I have(I pick them up from local PYP's when I find them and sell on the side) and installed it in the Tahoe. As soon as I turned the key to On, everything was different. Gauges powered up and zero'd out, all the typical lights went on and so at first, I thought my original cluster had died during the year of no use which seemed strange but you never know.
After verifying oil pressure was present on the gauge cluster, I reinstalled the fuel pump relay, plugged in the coils, drained the old gas(about 7g) and dumped some new fuel in it and it started right up. Great Success, in my best Borat voice! That made me happy after nearly a year of working on this thing on and off when time permitted. The builder that assembled the long block for me suggested 3 heat cycles of running the engine up to t-stat temp then letting the engine go cold, which I've done. The oil pressure is still pretty high, nearly 80 at cold start, and then drops to ~60 once warmed up. I haven't checked with the builder yet if it's expected and okay to have that high of oil pressure.

Back to the gauge cluster mystery....so after running the engine thru a few heat cycles, on a whim I reinstalled the original Tahoe gauge cluster. Turn the key to On got the same result of only the CEL on and nothing else. However, after starting the engine with that cluster installed, it's a whole different animal. About a half second after starting, the whole cluster comes back to life, all lights illuminate, gauges first zero out, and then read accurately to the engine running. So that must mean there is some sort of flash or short term memory, battery? in these clusters that after an extended period of time that battery or flash memory dies....until the cluster is powered back up by the vehicle. Anyone familiar enough with these to know with certainty what is at play here?

I also checked another 2500HD and Yukon Denali cluster that I have on the shelf that I thought were dead and needing repair. They as well only illuminated the background lights when bench tested with a 12v battery. Same result with these two, after the engine started they both came back to life as well and are fully functional once again. I'm wondering if I leave them in the vehicle for a week or so, if the flash-battery memory will return/recharge....gotta try that out once I start driving the Tahoe full time again.

 

[mattt]

Yesterday I drove the Tahoe for the first time but had to cut it short due to an idle issue it's having. On first start up when cold, it idles well. It seems like once it warms a bit(not at full operating temp) and goes into closed loop I'd assume, the idle deteriorates and if you blip the throttle as it returns to idle it will die at least 50% of the time. The idle continues choppy and then it throws a P0300(random misfire) and turns on the CEL. Maybe I just haven't run it long enough yet for the 'learn' to get everything in the sweet spot as far as idle?


On the first test drive yesterday, it was dying coming up to a stop sign or when off the gas for a spell, so I brought it back home until this is sorted out. It seems like I had read there are a few guys here that did a 6.0 swap and are running an unmodified 5.3 PCM on their rig, @Tonyrodz comes to mind? How is your idle if you care to weigh in? Interesting thing after the test drive yesterday...when I got back from the failed test drive I let it idle for 15-20 minutes and the longer it sat idling, it seemed to improve idle quality and upped itself into the 650-700rpm range. Initially it was trying to idle itself in the 550-600rpm range when it would deteriorate and go choppy. One thing I forgot to mention is the cam in there should be smooth and not choppy SUM8718 if I remember correctly. Any pointers, suggestions, etc from the excellent knowledge base of guys here with this issue? Thank you all in advance!

 

[Rocket Man]

I know Tonyrodz had his PCM flashed by a tuner. I’m not sure if you can run a 6.0 on a 5.3 tune but I doubt it. There’s a lot of differences. Running your PCM shouldn’t be an issue but I feel the tune file needs to be flashed. I’m not into tuning although I do have an HPT and plan on learning someday. Keep in mind I do not know for sure in your situation though.

 

[Mudsport96]

Well any aftermarket cam will need a tune to smooth out idle. Once you get it tuned, im sure the idle will be nice. But the factory tune can only adapt so much. That cam should make driving really nice with the added tq it will provide.

 

[Mudsport96]

I know Tonyrodz had his PCM flashed by a tuner. I’m not sure if you can run a 6.0 on a 5.3 tune but I doubt it. There’s a lot of differences. Running your PCM shouldn’t be an issue but I feel the tune file needs to be flashed. I’m not into tuning although I do have an HPT and plan on learning someday. Keep in mind I do not know for sure in your situation though.

You "can" run a stock 6.0 on a 5.3 tune, but it will never be ideal.
But he also has an aftermarket cam, so he needs a real tune anyway.

 

[Rocket Man]

You "can" run a stock 6.0 on a 5.3 tune, but it will never be ideal.
But he also has an aftermarket cam, so he needs a real tune anyway.

Yeah I realize you can run it on a 5.3 tune just like I was able to run a stock tune on my 4.8 after I did a cam swap but it ran like crap and threw codes. I’m thinking that’s what his issue is currently.

 

[Tonyrodz]

My 03 came originally with the 4.8. When it was swapped to the 6.0, it was tuned by the guy who did the swap. It ran great for a little bit, but other issues are going on with it that I'm still trying to sort out. I never had an idle issue tho. It idles somewhere around 700 or so. I agree with the above statements with the tune. If you're not tuned for the 6.0--you're running on a 5.3 tune, you're not getting everything you can out of it. It will run, but might run like crap. If I was you I'd go to a reputable tuner, who's familiar with the LS platform and get a dyno tune. Without the tune for the bigger motor, you'll never be happy with it. Why go bigger on the motor and choke it with the 5.3 tune?

 

[rockola1971]

Instrument Cluster has either silver migration going on, connector at rear is corroded and/or the receiving male connection on the IC or a busted solder joint on the IC...or a combination of the 3. These are the most common problems with GM IC's. Pull the plastic covers off the cluster board and inspect for green, gray or white "dusting". Its silver out of the solder corroding. Clean whole board with rubbing alcohol and a wash rag or old white sock. Be gentle. We arent scrubbing the thing like trying to get paint off a old car. Inspect for cold solder joints which will have circles in the middle of them that are little cracks. Clean connection at rear of board and dont forget the connector (truckside harness). All soldering should be done with lead/tin based solder which will lower melting point of current solder on board.

 

[mattt]

Thank you all for commenting and providing .02 cents. Let me clarify, I plan to have it tuned by a dyno shop pro at some point in the future. I was hoping it would run well enough in the mean time so I could drive it to the trans shop for a rebuild and then drive to the dyno guy as well. The engine is all new, but the I'm still on the original transmission with 335k on it, so that is up next. I will likely be swapping intakes as well to either of the two intakes(old truck intake or nnbs) I have that use the larger 87mm 4 bolt throttle body. For all of these reasons I'm trying to delay a full tune until it is done, done. I hear all of you that the 5.3 tune will be a disservice to a 6.0 and I agree. @Tonyrodz what sort of other issues are you chasing down now?

Another reason I have to get it tuned is I added e-fans at the same time and they're currently just running off a toggle switch with both fans running high. Since I'm in CA, I am trying to sort out the best way to deal with the tune issue since the bi-annual inspection is apparently now checking for 'checksum' when plugged in to see if the tune has been altered. If only GM had produced a Flex Fuel capable, gen 3 6.0 lq4/9 with e-fans, it would be so easy as to just run a factory configured tune from one of those vehicles.

Thanks rockola, I will pop the cover off and check solder joints. It's still astounding that my original cluster gave up the ghost just sitting there not being used for the last year.

 

[Tonyrodz]

Thank you all for commenting and providing .02 cents. Let me clarify, I plan to have it tuned by a dyno shop pro at some point in the future. I was hoping it would run well enough in the mean time so I could drive it to the trans shop for a rebuild and then drive to the dyno guy as well. The engine is all new, but the I'm still on the original transmission with 335k on it, so that is up next. I will likely be swapping intakes as well to either of the two intakes(old truck intake or nnbs) I have that use the larger 87mm 4 bolt throttle body. For all of these reasons I'm trying to delay a full tune until it is done, done. I hear all of you that the 5.3 tune will be a disservice to a 6.0 and I agree. @Tonyrodz what sort of other issues are you chasing down now?

Another reason I have to get it tuned is I added e-fans at the same time and they're currently just running off a toggle switch with both fans running high. Since I'm in CA, I am trying to sort out the best way to deal with the tune issue since the bi-annual inspection is apparently now checking for 'checksum' when plugged in to see if the tune has been altered. If only GM had produced a Flex Fuel capable, gen 3 6.0 lq4/9 with e-fans, it would be so easy as to just run a factory configured tune from one of those vehicles. Friggin unelected bureaucRATS abusing their power in that regards. If it blows clean & has smog equipment on it, then it's passes is how it should be.

Thanks rockola, I will pop the cover off and check solder joints. It's still astounding that my original cluster gave up the ghost just sitting there not being used for the last year.

Some days it runs great, some days it runs like crap. And for some odd reason it'll sporadically just shut off as my gf is driving it. It'll just happen, doesn't give any hints that it's gonna shut off. Hasn't happened to me yet. No codes appear either.